1. Field of the Invention
The present invention generally relates to a fuel injected internal combustion engine. More specifically, the present invention relates to a fuel injected internal combustion engine with direct fuel injection into the combustion chamber and spark-ignition.
2. Background Information
An example of a fuel injected internal combustion engine with direct fuel injection into the combustion chamber and spark-ignition is disclosed in Japanese Laid-Open Patent Publication No. 2000-227028. In this publication, a fuel injection valve is positioned at the periphery of the combustion chamber and a cavity is formed in the top of the piston. The fuel injection valve injects a relatively thin, roughly fan-shaped stream of fuel toward the cavity and a spark plug ignites the resulting fuel-air mixture.
The cavity has a bottom wall and an opposing side wall. The opposing side wall has a section that, in a plan view, forms a portion of an ellipse whose foci are located at the injection vent of the fuel injection valve and close to the spark plug, respectively. The shape of the cavity causes the roughly fan-shaped fuel to first follow the bottom wall as it spreads and then follow the opposing wall such that it converges in the vicinity of the spark plug. Thus, a fuel-air mixture field is formed close to the spark plug.
Fuel injection valves are known that have a nozzle portion with an injection vent shaped like a slit. This type of fuel injection valve injects fuel in the shape of a relatively thin fan. The fuel stream from this slit-type injection valve generally has strong penetration. Thus, a fuel-air mixture field can be formed using the motion of the fuel stream alone, i.e., it is not necessary to utilize the gas flow inside the cylinder to form the fuel-air mixture field.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved fuel injected internal combustion engine with direct fuel injection into the combustion chamber and spark-ignition. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
It has been discovered that the fuel stream sprayed from such a slit-type injection valve is relatively easily affected by the flow of gases inside the cylinder. The reason the fuel stream is easily affected by the flow of gas inside the cylinder in spite of its strong penetration is believed to be that the fuel stream divides the space surrounding the fuel stream horizontally into upper and lower sections and the pressure difference between the upper and lower sections of space (the pressure changes in various ways due to the flow of gases inside the cylinder) greatly affects the fuel stream.
Since it is normal for the flow of gases inside the cylinder to be different for each cycle, the relationship between the fuel stream and the cavity changes each cycle and there is the possibility that the position and size of the fuel-air mixture field will be unstable. One object of the present invention is to resolve this issue.
The forgoing object of the present invention can basically be attained by providing a direct fuel injection engine comprising a combustion chamber, a spark plug and a fuel injection valve. The combustion chamber has a piston movably mounted therein. The piston includes an upper wall having a cavity with a fuel stream directing surface. The spark plug has a spark discharge gap arranged to ignite a fuel-air mixture in the combustion chamber. The fuel injection valve includes a front edge portion with a plurality of injection vents arranged and configured to directly inject fuel into the combustion chamber against the fuel stream directing surface as plurality of solid-core fuel streams that strike at non-perpendicular angles. The fuel stream directing surface is at least partially curved to direct movement of the fuel streams after striking the fuel stream directing surface toward the fuel injection valve. The fuel stream directing surface is partially elliptical in a top plan view with its focal points being located at the front edge portion of the fuel injection valve and at the spark discharge gap of the spark plug as its focal points.
These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention.